The present invention relates to a device for determining at least one parameter of a flowing medium.
A hot-wire sensor for measuring gas volume flow, which is positioned in a bypass channel, in which there is a wall surface downstream from the opening of the bypass channel that runs parallel to the opening of the bypass channel, is described in German Published Patent Application No. 41 06 842. The sensor is not positioned in a shadowed region of the bypass channel, however, and is therefore not protected from soiling.
An air flow meter, which includes a separation point or a separating wall in the bypass channel, is described in European Patent Application No. 0 803 712. Furthermore, there is a wall in the bypass channel that is parallel to the inlet opening of the bypass channel and also completely covers this opening. The sensor is not protected from liquids flowing in, however.
A measuring device for measuring the mass of a medium flowing in the line is described in German Published Patent Application No. 198 15 654, in which there is a separation point or separating wall in the bypass channel that is intended to protect the measuring element from solid particles and other impurities. However, due to the reflections of the solid particles that hit an inner wall in the bypass channel, these are reflected into the measuring channel and may hit the measuring element there.
There is no indication that one may, on the basis of the law of reflection, influence the reflections of solid particles by changing the inner wall.
A bypass geometry is described in a publication, in which there is a separating wall in the bypass channel that extends parallel in the flow direction, and there is a wall surface that runs parallel to the inlet opening of the bypass channel The wall surface lies downstream of the measuring element.
Here, the measuring element is protected from the main flow by the separating wall and a lower inlet opening.
The varying course of the main channel and the measuring channel results in increased signal noise. In case of backflow, liquids, particles, and oil may directly reach the measuring channel and may soil or destroy the measuring element.
The device according to the present invention may provide the advantage that the at least one measuring element is protected from the impingement of liquids and particles in a simple manner.
It may be advantageous if the inlet opening of the bypass channel includes a rough edge for liquids, because in this manner, a liquid wall film, which may possibly reach the measuring element, may no longer form in the bypass channel in the region of the inlet opening.
The outlet opening of the bypass channel may advantageously be oriented laterally, downward, or in the flow direction.
The separating wall may advantageously include at least one U-shaped section, in order to protect the sensor in this manner during forward flows as well as backflows.
Example embodiments of the present invention are illustrated in simplified form in the drawings and explained in greater detail in the following description.